When a plurality of devices such as storage devices or the like are multistage-connected, a connection expansion device is used for connection expansion. For example, as multistage-connected SAS devices, SAS expanders are used for connection expansion. After being connected to the expander, an input-output (I/O) controller, which is a higher-level device of the expander, recognizes all devices controlled by the I/O controller by performing a state confirmation processing, called “Discovery”, through the expander. The Discovery processing includes device recognition processing used for recognizing the state of a device, and in the device recognition processing, device abnormality such as a device failure, disconnection, or the like is recognized.
Usually, in such a storage system as described above, a configuration is adopted in which SAS devices are multistage-connected, information setting is performed on the SAS expanders, and the extraction of failure information and the like are performed. One of examples of the related art is Japanese Laid-open Patent Publication No. 2008-242872.
Incidentally, in the multistage connection configuration, when abnormality or the like occurs in a device controlled by a specific expander, and hence a configuration change occurs, the specific expander is put into a Configuring state. However, an expander other than the specific expander is also put into a Configuring state. In this case, it is difficult for the I/O controller to perform an I/O issue for a device controlled by the expander in the Configuring state. Namely, it is impossible to perform input-output access on the device controlled by the expander in the Configuring state.
In such a state described above, a multistage connection environment deteriorates, and the number of unusable devices increases if the scale of the multistage connection is large. Therefore, it is difficult to gain the benefit of the multistage connection environment.